1. Field of the Invention
The embodiments of the present invention relate to a vibration characteristics measurement apparatus and method for measuring vibrations produced in a suspension or the like of a hard disk drive (hereinafter referred to as an HDD).
2. Description of the Related Art
An HDD has been used for a wide range of applications by a wide range of users. For this reason, the HDD may be used in harsh environments, and thus high reliability of impact resistance is required. Improvement of the impact resistance performance therefore has been required more strongly than ever before.
The HDD incorporates a suspension to write and reproduce information to and from a rotating disk. The suspension is provided at the tip portion of an arm, and a slider that constitutes a magnetic head is provided at the tip portion of the suspension. When the HDD receives an impact, forcing the slider and the suspension into contact with a disk and leaving a flaw on the disk surface, it may lead to performance degradation of the HDD. Thus, the behaviors of the slider and the suspension need to be evaluated when the HDD receives an impact. The conventional methods of evaluating the impact resistance of the HDD slider and suspension include the following published technologies:
(1) Observation of the behavior of the slider during an impact by use of a high-speed camera;
(2) Measurement of the behavior of the slider during an impact by use of a Doppler vibration meter (see Jpn. Pat. Appln. KOKAI Publication No. 2007-192735, for example);
(3) Observation of a flaw created on a disk surface after an impact; and
(4) Observation of changes in the distance between the slider and a disk during an impact through the observation of dynamic changes in the capacitance (see A Novel HDD “Component-Level” Operational-Shock Measurement Method [IEEE Transaction of Magnetics, Vol. 43, No. 6, June 2007], for example).
According to the evaluation methods 1, 2 and 3, how much the slider is lifted from the disk because of the force of the impact (slider lift-off level) is measured. The lift-off amount of the slider, however, is as small as the order of 10 nm, and thus it has been very difficult to accurately evaluate a level at which no lift-off of the slider occurs, i.e., whether there is any slight change in the lift-off amount of the slider and whether the slider makes contact with the disk during the impact. Furthermore, it has been difficult to measure any change in the distance between the slider and the disk during the impact when the HDD is operating.
Moreover, according to the technology (4) of observing the capacitance, the HDD is connected to a capacitance meter, which tends to be a test that utilizes costly general-purpose measurement devices in combination. The capacitance can be measured by a general LCR meter. However, the measurement speed of a commercial LCR meter that is designed to measure a static capacitance is 200 Hz (5 ms) at most. For this reason, it is difficult to measure the behavior of a slider having a vibration frequency of 100 to 200 KHz through a change in the dynamic capacitance with such a meter.
Hence, a vibration characteristics measurement apparatus and method that can accurately measure vibrations caused in the suspension or the like of the HDD during an impact have been demanded.